We have demonstrated that AIDS-associated Kaposi's sarcoma (KS) cells express IL-4 receptors. These receptors are functional because IL-4 inhibited the growth of these cells in tissue culture. KS cells are known to produce IL-6 and Oncostatin-M and they proliferate in an autocrine manner to these cytokines. IL-4 inhibited the production of both cytokines. These observations suggest that IL-4 can be a useful lymphokine for the treatment of KS.